What are you basing that statement on? Have you driven a 2554?

You will if it was there. I had a 2554 then switched to a built motor with a 2560. I find myself shifting at higher RPM when puttering around town in the 2560 than the 2554. I liked the 2554 better for daily driving. The 2560 is a compromise to get more peak power. There is a definite softness to the boost response in the 2560 in the 3500-4000 RPM range which isn't there in the 2554.

There's a pleasantness to having a very wide torque band which is there in my 540i, and which the 2554 was better at than the 2560.

Yes you can see it on the dyno by plotting torque vs. time and you hold an RPM at light throttle then floor it.

And unless the same person drives the 2 turbos then the only way to compare 2 different setups is through datalogs.

I've driven both turbos. My subjective opinion is that the EFR responds better than every Garrett setup I've driven, including my old BP4W/2554R setup. I agree that the 2560R is a softer turbo, and the 2860RS is softer again (IMO that turbo is too big for a 1.6 and as large as I would ever go for a 1.8 street car, having owned a 2871R). The 6258's spool was as good or better than my 2554R setup was, and the transient response was better.

However your 2554 was on an NA 1.8, and the EFR6258, on a VVT, correct?

VVT spools > 99/00 > NA 1.8

The EFR I drove was on a BP05 and it was essentially untuned. It was still as good as my polished BP4W/2554R setup.

Do not run an EFR6258 on a stock block! Even with the "low boost" actuator set with minimal preload i was not able to keep it below 8psi. It broke a rod at the first autocross this year.

8psi = 200ft.lbs at most. If you broke a rod at 200ft.lbs, it was the tune, not the turbo.

Did you have EBC working and tuned ? I can keep 10psi on the medium boost canister w EBC (for the reccord i did not try cold weather or lower boost settings)

So far no one has been able to run EFR6258 on stock block without blowing it up :fael:

The guy who built your setup had no problem doing it :party:

Agreed, i said i was not able to keep it to 8psi...

That autox was below 45*F air temp in Maryland. First run was able to keep to 8psi, but 2nd and 3rd run were not able to keep it below 10psi. A stock engine could have probably held that power if it was in a little bit better condition. This engine already had 120k on it with 60k above 200hp from my old BEGI turbo.

The point is that EFR turbo does not belong on a stock engine...

Then your EMS4 basemap timing is more aggressive than I thought. This was on a minimally pre-loaded 7psi actuator it creeped to 10psi at peak torque and more or less on your timing and vvt maps (putting a car with electrical problems the dyno is some expensive troubleshooting), lol. I think 8psi on the 6258 or 6758 EFR is going to be worth more than 200ftlbs with a more aggressive timing map.

https://www.miataturbo.net/attachmen...ine=1371503403

We all know that EFR on stock block is on thin ice at best, why even waste time arguing about it?

Anything at all outside ideal circumstances happens, and boom.

Exactly!!!

Now who wants to build me a new block...?:facepalm::facepalm::facepalm:

200ft.lbs is based on BMEP calculations, not on a wild-ass guess. Miatas generally don't make more than ~72lbs of torque per liter per atmosphere of pressure. 8 PSIg = ~1.54bar * 1.84L * 72lb/L-ATM = 204ft.lbs. You can see where the torque levels out at ~5k before beginning to creep again, and it levels out at 195ft.lbs. That's exactly what I would expect an EFR6258 to make at ~7psi.

And thats 200ftlbs on a low reading dynapac, which would be closer to 220 on a dynojet.

Thank you for this! I've been between these exact two choices for a while.

For me personally its either, EFR$$Custom$$, or Begi S6 iron mani down the street with tial vband gtx2863, support is close by if anything goes wrong.

But dat low end EFR spooool :drool:

This thread actually had the best actual comparison data I've seen. Are there any others?

https://www.miataturbo.net/diy-turbo...cussion-79576/

And I ran a defective EFR for a month... its just a matter of time. Evan ran his setup for just 2 months on stock motor.

I'm currently sitting on a 6258 so I've had a good time following this thread.

This sums up my thinking exactly. I'm going to try my best not to do my install until there is a built motor between the frame rails. I have no doubt that someone with careful planning, experience and knowledge of how these systems work would be able to keep things "stock block" compliant, but I'm not that person. I see no reason to run a baller manifold & $$$ turbo that'll do 44lbs/min at something silly like 5~6psi to preserve the stock block.

If all you want is 200/200 and epic spool, go buy a FMII & 2554.

And that's the way it looks like it's gonna go... the kit was sold to another member who pm'd the seller before I did... but for $2500, that woulda been one hell of a setup.

But you are right, no sense in attempting to tame that beast for the sake of a stock block...(and probably failing at that, too.)

It is kinda lame that the FMII kit is gonna cost me more tho, that's the part I don't like.